Injection involves ajagged or sharp object that has been contaminated with a toxic material creating or entering an open wound in the skin. The poison enters the bloodstream once injected into the skin. The exposure method may greatly impact the severity of the damage produced. A chemical that is extremely poisonous by one route of exposure may have little, any, effect by other routes. For example, carbon monoxide is toxic by inhalation. Just 1% concentration in air, if inhaled, is fatal in 1 min. However, you could stay in a 100% concentration indefinitely provide there was an outside air supply, such as self-contained breathing apparatus (SCBA). Carbon monoxide is not absorbed through the skin. Rattlesnake venom is poisonous if it gets in the bloodstream; it damages the cells. If must be injected to cause damage. If ingested, it may cause nausea, but it will not enter the bloodstream.